.mask {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  bottom: 0;
  background-color: rgba(0, 0, 0, 0.4);
  display: flex;
  justify-content: center;
  align-items: center;
}

button.close-btn {
  width: 300px;
  height: 80px;
  font-size: 30px;
  font-weight: bold;
  color: #ffff;
  outline: none;
  border: none;
  background-color: skyblue;
}